1. Field of the Invention
The present invention relates to a printing apparatus that can execute a cleaning mode for a platen.
2. Description of the Related Art
In an inkjet printing apparatus, a platen for supporting a sheet can be stained with ink mist generated during printing or ink discharged outside the sheet. If printing continues with the platen stained, the stain can adhere to the rear surface of the sheet.
In order to solve the problem, as discussed in Japanese Patent Application Laid-Open No. 2004-025666, a cleaning sheet that easily absorbs ink is provided, the cleaning sheet is passed through a conveyance path, and conveyance is controlled to reciprocate the sheet leading edge on the platen. Thus, the leading edge of the cleaning sheet wipes the surface of the platen to remove the stain.
In a typical printing apparatus, a plurality of conveyance rollers is arranged on a conveyance path on which a sheet is picked up from a sheet feed unit and the sheet is conveyed to a printing unit. In the configuration, when cleaning a platen by the reciprocation as discussed in Japanese Patent Application Laid-Open No. 2004-025666, the trailing edge of the cleaning sheet that is sent back hits a conveyance roller without properly being nipped by the conveyance roller. Thus, the sheet trailing edge can be folded or a sheet conveyance jam can occur.
In particular, the problem can become serious when a plurality of conveyance rollers is rotated by a shared single motor to downsize an apparatus and pursue cost reduction. In the configuration, conveyance rollers near the printing unit are rotated forward or backward according to a rotational direction of the motor, but conveyance rollers on the upstream side thereof are rotated only forward, irrespective of the rotational direction of the motor.
In the configuration, when cleaning the platen by the reciprocation as discussed in Japanese Patent Application Laid-Open No. 2004-025666, when the trailing edge of the cleaning sheet, sent back by rotating backward the conveyance roller on the downstream side, reaches the conveyance roller on the upstream side, the conveyance roller on the upstream side is rotated forward. Therefore, the sheet hits the conveyance roller without being nipped, thus increasing the possibility that the sheet trailing edge is folded or the sheet conveyance jam occurs. If the platen cleaning is started when the sheet is nipped by both the conveyance rollers on the upstream and downstream sides, the sheet feed direction is different between the rollers on the upstream and downstream sides. Therefore, the sheet can sag in the middle thereof and the sheet conveyance jam can occur with a high possibility.
Also as discussed in Japanese Patent Application Laid-Open No. 2004-025666, the leading edge of the cleaning sheet is reciprocated on the platen. If the cleaning sheet in use curls upward, the sheet leading edge floats up and does not come into contact with the platen. This reduces a cleaning effect. If the sheet leading edge further floats up, the sheet leading edge can hit a print head. This is because the sheet is held only by the conveyance roller on the upstream side in the printing unit, and the sheet is reciprocated in an unstable conveyance state.